1. Field of the Invention
The present invention relates to a method for producing a magnetostrictive element and a magnetostrictive element, more particularly a method for producing a magnetostrictive element which contains Sm and a transition metal element.
2. Description of the Related Art
Magnetostriction is a phenomenon of a ferromagnetic material to undergo a dimensional change when magnetized, and a magnetostrictive material is a material which exhibits this phenomenon. Saturation magnetostrictive constant, which represents a dimensional change at saturation by magnetostriction, is generally in a range from 10−5 to 10−6, and a magnetostrictive material having a high saturation magnetostrictive constant is sometimes referred to as a giant-magnetostrictive material. These materials are widely used for vibrators, filters, sensors, and the like.
At present, a magnetostrictive material based on a laves type intermetallic compound of RFe2, which is a compound of R (rare-earth element) and Fe, is known to have a high saturation magnetostrictive constant (refer to U.S. Pat. Nos. 3,949,351, 4,152,178, 4,308,474 and 4,375,372). These materials, however, involve problems of insufficient magnetostrictive value in an external magnetic field of low intensity, although exhibiting a high value when applied to a magnetic field of high intensity. Therefore, magnetostrictive materials based on a laves type intermetallic compound of RFe2 have been studied to have a higher magnetostrictive value even in an external magnetic field of low intensity, and it is proposed to orient the material along the [111] axis as an easy-magnetization axis of high magnetostrictive constant. Magnetostrictive materials based on a laves type intermetallic compound of RFe2 exhibit a high magnetostrictive value at a composition of Tb0.3Dy0.7Fe2.0 (atomic ratio), and this composition has been used exclusively.